The present invention relates to apparatus for perforating wrapping material for cigarettes, filter rod sections or analogous rod-shaped articles which constitute or form part of smokers' products. More particularly, the invention relates to improvements in apparatus for making holes in webs, sheets, strips or like bodies of wrapping material by resorting to electrodes which define one or more spark gaps. Still more particularly, the invention relates to improvements in apparatus wherein the wrapping material is in motion during exposure to the action of perforating means and which can perforate wrapping material for use in machines which manufacture and/or process rod-shaped articles which constitute or form part of smokers' products.
It is already known to make holes in a running web of wrapping material for cigarettes or the like by resorting to one or more pairs of electrodes which define one or more spark gaps and by causing the running web to pass through such spark gap or gaps while the electrodes generate sparks which burn holes into the wrapping material therebetween. It is advisable to install the perforating apparatus directly in a machine which makes and/or processes cigarettes or the like because this renders it possible to adjust the perforating apparatus in response to signals which are generated during testing of finished products in the machine proper, e.g., during testing of the wrappers and/or tobacco-containing ends of filter cigarettes and/or during testing of the resistance of filter cigarettes to axial flow of gaseous fluid therethrough. Thus, if a perforating apparatus is installed directly in a filter tipping or like machine, its perforating action can be adjusted in immediate response to detection of articles whose wrappers exhibit excessive or insufficient permeability to the flow of a gaseous fluid therethrough. The reason for making holes in the webs of wrapping material for cigarettes or the like is that many manufacturers attribute highly beneficial effects to atmospheric air which can flow through the perforations of the wrapping material to be mixed with the column of tobacco smoke before such column reaches the smoker's mouth and lungs. The admixed atmospheric air is supposed to reduce certain deleterious effects of nicotine and/or condensate in tobacco smoke.
It has been found that many presently known perforating apparatus which resort to pairs of electrodes (i.e., which rely on the generation of sparks for the making of holes in a running web of cigarette paper or the like) cannot be installed in a filter tipping or like machine for a variety of reasons. Thus, an electrically operated perforating apparatus generates relatively large quantities of dust which develop as a result of combustion of wrapping material in the spark gaps between neighboring electrodes. Moreover, such mode of making holes in cigarette paper or the like entails the development of substantial quantities of ozone which can exert an adverse influence on the health of the attendants. Still further, improper operation of such apparatus can result in charring or total combustion of the running web of wrapping material.